This invention relates generally to a modified copolymer of a polymerizable olefin and an .alpha.,.beta.-ethylenically unsaturated carboxylic acid contacted with a cyclic iminoether compound. Further, this invention relates to the use of this modified copolymer as an improved adhesive for forming laminates of plastic materials, or plastic and metal.
The use of thin film laminates is quite common especially where impermeability to gas, water or light is desirable. In one particular embodiment, laminates are used as food wraps to preserve their freshness. However, regardless of the use for a laminate, good adhesion of the various laminate layers is essential.
One family of adhesives commonly employed to adhere laminates are those formed from a polymerizable olefin and an .alpha.,.beta.-ethylenically unsaturated carboxylic acid such as ethylene acrylic acid as disclosed in U.S. Pat. No. 3,442,745. This group of copolymers is known in the art to be useful as an emulsion or hot melt adhesive for laminates. Despite their acceptance as an adhesive, it would be a useful improvement to increase adhesion, especially to plastics, in order to increase the integrity and applicability of laminates made therefrom.
A process for improving the adhesion of a copolymer adhesive is the subject of this invention. In particular, the ring-opening characteristic of a cyclic iminoether, such as an oxazoline ring, which is generally known in the art (E. M. Fry, J. Org. Chem., 15 802 (1950)) is employed to form a modified copolymer which surprisingly exhibits improved adhesion, especially to plastics.